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Avalanche Forecast

Archived

Mar 4th, 2023–Mar 5th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Wind slabs remain reactive to human triggering. Watch for wind loaded features in the alpine and at treeline.

Confidence

Moderate

Avalanche Summary

Ski hills are still reporting wind slabs being reactive to skier/boarder traffic up size 1.5 in lee aspects at all elevations. Several cornices failures to size 2 have also been reported in the last 24/48h. Recent natural activity has also been observed on the basal facets in the last 24h, up to size 2.5

Snowpack Summary

The alpine and exposed regions at treeline are wind effected and have windslabs which remain active to human triggering. Steep solar slopes at treeline and below may also have a thin sun crust. The wind slabs overlie the various Jan PWL interfaces of sun crusts, facets, and surface hoar down 65-120 cm. The weaker Nov. 16 basal facet layer is down 50-200 cm and produces moderate to hard sudden collapse results. Deeper snowpack areas west of the divide are stronger and more supportive than areas to the east.

Weather Summary

Saturday Evening: An upslope front could bring 5cm's to the eastern regions of the park, as overnight lows drop to -15/-20.

Sunday: Expect a mix of sun and cloud with trace amounts of snow through the day. Winds will be SE to S at ridgetop, avg. 20-30 km/h with gusts in some areas to 50km/h. The daytime high in the alpine is forecast to be -10.

For a more detailed weather forecast, click here.

Terrain and Travel Advice

  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.